CaMK4 compromises podocyte function in autoimmune and nonautoimmune kidney disease
Kayaho Maeda, … , Maria G. Tsokos, George C. Tsokos
Kayaho Maeda, … , Maria G. Tsokos, George C. Tsokos
Published July 9, 2018
Citation Information: J Clin Invest. 2018;128(8):3445-3459. https://doi.org/10.1172/JCI99507.
View: Text | PDF
Research Article Autoimmunity Nephrology

CaMK4 compromises podocyte function in autoimmune and nonautoimmune kidney disease

Abstract

Podocyte malfunction occurs in autoimmune and nonautoimmune kidney disease. Calcium signaling is essential for podocyte injury, but the role of Ca2+/calmodulin–dependent kinase (CaMK) signaling in podocytes has not been fully explored. We report that podocytes from patients with lupus nephritis and focal segmental glomerulosclerosis and lupus-prone and lipopolysaccharide- or adriamycin-treated mice display increased expression of CaMK IV (CaMK4), but not CaMK2. Mechanistically, CaMK4 modulated podocyte motility by altering the expression of the GTPases Rac1 and RhoA and suppressed the expression of nephrin, synaptopodin, and actin fibers in podocytes. In addition, it phosphorylated the scaffold protein 14-3-3β, which resulted in the release and degradation of synaptopodin. Targeted delivery of a CaMK4 inhibitor to podocytes preserved their ultrastructure, averted immune complex deposition and crescent formation, and suppressed proteinuria in lupus-prone mice and proteinuria in mice exposed to lipopolysaccharide-induced podocyte injury by preserving nephrin/synaptopodin expression. In animals exposed to adriamycin, podocyte-specific delivery of a CaMK4 inhibitor prevented and reversed podocyte injury and renal disease. We conclude that CaMK4 is pivotal in immune and nonimmune podocyte injury and that its targeted cell-specific inhibition preserves podocyte structure and function and should have therapeutic value in lupus nephritis and podocytopathies, including focal segmental glomerulosclerosis.

Authors

Kayaho Maeda, Kotaro Otomo, Nobuya Yoshida, Mones S. Abu-Asab, Kunihiro Ichinose, Tomoya Nishino, Michihito Kono, Andrew Ferretti, Rhea Bhargava, Shoichi Maruyama, Sean Bickerton, Tarek M. Fahmy, Maria G. Tsokos, George C. Tsokos

×

Figure 3

Podocyte-targeted delivery of KN93 suppresses kidney disease development in lupus-prone mice.

Options: View larger image (or click on image) Download as PowerPoint
Podocyte-targeted delivery of KN93 suppresses kidney disease development...
MRL.lpr mice were injected i.p. with free KN93 (10 μg/wk), anti-podocin or anti-nephrin antibody–coated KN93-loaded nlg (10 μg of KN93/week), or empty nlg at from 8 to 16 weeks of age (n = 5–7 mice in each group). (A) Urine albumin/creatinine (Alb/Cre) ratio. Urine samples were obtained biweekly, and albumin and creatinine levels were determined by ELISA. Error bars represent mean ± SEM. *P < 0.05, 2-way ANOVA with Bonferroni’s post test. (B and C) Representative images of glomeruli from 16-week- old MRL.lpr mice treated with anti-nephrin antibody–coated empty nlg or KN93-loaded nlg. PAS (B) and Masson’s trichrome staining (C) are shown. The arrows point to the crescent. Scale bars: 50 μm. (D) Mean histological scores in the kidneys of mice from the indicated treatment groups (n = 5 in each group). *P < 0.05; **P < 0.01, Student’s t test. (E and F) Electron microscopic images of a glomerulus from a mouse treated with anti-nephrin empty nlg (left) showing diffuse podocyte foot process (FP) effacement with slit diaphragm occlusion (arrows) and subepithelial dense deposits (asterisks) and a mouse treated with anti-nephrin KN93-loaded nlg (right), which shows podocytes with normal foot processes and slit diaphragms and no deposits in the basement membrane. Original magnification, ×8,000 (E); ×30,000 (F). Three glomeruli were evaluated in each of 3 mice in each experimental condition. (G) C3 and IgG deposition was significantly suppressed in the glomeruli of MRL.lpr mice treated with KN93 targeted to podocytes, as indicated. Kidney sections from MRL/MpJ (16 weeks of age) mice are shown as controls (n = 5 mice in each group). (H) Nephrin (green) and synaptopodin (red) expression detected by immunofluorescence. Scale bars: 50 μm. (I) The fluorescence intensity of nephrin and synaptopodin quantified in glomeruli from mice subjected to the indicated treatments. ****P < 0.0001, Student’s t test. (J) Nphs1, Nphs2, and Synpo expression in glomeruli from mice treated with anti-nephrin–coated empty or KN93-loaded nlg. Results were normalized to the expression of GAPDH (n = 5 in each group). ****P < 0.0001, Student’s t test.